The quality of the Grand Valley’s air has been improving, in general, for the past seven years. But on those rare days when the air does get bad — typically during cold-weather inversions — it is getting really bad.

Those are the conclusions that Michael Brygger, an air quality specialist for Mesa County, has derived from the latest state air quality report, produced by the Colorado Department of Public Health and Environment.

Brygger said the report indicates that the annual average amount of particulate matter in the air has been declining steadily. Particulate matter is a mixture of microscopic solids and liquid droplets suspended in the atmosphere, according to the state health department.

“The improvements are attributable to automobiles over the years,” he said.

Although the valley has had a growing population and more vehicles in the past decade, the improvements in engines and fuels have helped keep the air clean, he said.

But don’t start breathing easy just yet.

“We are having more episodic events,” Brygger said.

There are two basic kinds of “episodic events.” The first kind is dust storms. These events can carry dust, generally about 10 micrometers in size, into the valley from the deserts.

“Small particles, less than 10 micrometers in diameter (about 1/4 the size of a grain of salt), pose the greatest problems,” according to the state report. “The smallest particles (generally about 2.5 micrometers in size) can get deep into the lungs, and some may even get into the bloodstream.”

Valley residents are not totally at the mercy of wind driven events. There are plenty of air-pollution sources here in Mesa County that can be controlled, among them dust from construction sites, road dust and agricultural activities that include burning, tilling and harvesting.

Valley residents also can take charge of their air and at least partially mitigate the power of the second kind of “episodic event” Brygger referred to: the temperature inversion.

An inversion occurs when cold air is trapped close to the ground by a blanket of warm air. The cold air behaves like a bubble, trapping all the pollutants. Normally, this smog would be whisked out of the valley by the wind, but during an inversion the smog builds into a brown cloud.

“Our winter inversions are getting worse,” Brygger said.

Brygger looks at the state report on air quality, released in August, as an opportunity to educate valley residents about the situation.

Brygger suggests that during an inversion people reduce driving and do not idle their vehicles in the morning before work or use wood burning stoves.

He said people with wood burning stoves can make use of the Housing Resources of Western Colorado wood stove exchange program.

Brygger also urges residents to participate in the county’s regional and transportation planning process, as motor vehicles are a prime contributor to air pollution.

“That is an opportunity for everybody in the county to provide input on transportation in the area, and (transportation) by far has the greatest impact on air pollution in the county,” he said.

Much of the particulate matter wafting through the air during an inversion is 2.5 microns in size, which is typical of smoke and haze.

“They are fine enough to get all the way down into the deep recesses of your lungs,” he said.

More people moving into the valley will put even greater challenges to maintain clean air, but now is the time to plan for the future, he said.

“We are becoming much denser, and the urban plan is to force density to increase rather than sprawl. We need to be sensitive to our neighbors’ health,” Brygger said.